Specialisation Research – Rendering

“Rendering is the name given to the process in three-dimensional graphics whereby geometric description of an object is converted into a two-dimensional image-plane representation that looks real.” – Allen Tucker (mathematician)

Rasterisation

Most game engines use this technique for real time renders.-Lighting not as accurate (approximate) compared to ray tracing
-Instant result

Ray Tracing

-Ray tracing is a rendering technique which is capable of creating photo realistic images from three dimensional scenes.
-This process involves calculating the path of ever single light ray that hits a pixel of the screen.
-This takes some serious computing power because the path of light may bounce of multiple objects.
-The calculations must be made for every light in the scene. (Not suitable for real time rendering)
-The positive side of this means indirect lighting is occurring which helps the scene look real.

The key with a ray tracer is not its complexity but the complexity of its optimisations and implementation.

Created by Turner Whitted in 1980 (36 years ago).
Tracing rays of light allowing reflection and refraction.
The resolution is 512 x 512 and took an hour and 14 minutes to render.
Todays computers are capabile of reproducing this scene in real time.

Radiosity

-Similar to ray tracing but uses different algorithms to calculate the light bounces.
-Often used in architectural renders due to the effectiveness of recreating natural shading.

In the image above there are two identical scenes. They are rendering with a single point light set up out side the room for a single direct illumination (simulating the sun).
They both use ambient lighting in the scene.
One of the scenes is rendered with Radiocity and one is rendered without.
-The scene using Radiocity collects shadows a lot more effectively in the corners of connecting walls not to mention they are much softer.
-The Radiocity also allows the colour of the red carpet to bleed onto the grey walls.

How to cheat the system?!?

Above are some beautiful examples of the different algorithmic types of rendering and the visuals they can produce. They can be extremely taxing for a computer to replicate.
So other ways of reproducing similar images in real time have been developed to ‘cheat’ the system if you will.

Light mapping

Light mapping Is commonly use in games on static objects to give the illusion of high resolution lighting or indirect lighting.
The process involves baking the lighting information onto a light map allowing the creator to then import it onto the model as part of a texture.

The down side to this is once the lights have been baked on the model, the lights in the scene aren’t allowed to move because the shadows on the model will not update.

Environment mapping

Advanced render man –
“In Toy Story, for example, Buzz Lightyear’s plastic helmet reflected only three objects or note:
-a pre-rendered image of the room he was in, quite blurry
-Woody’s face when he was near, sharply
-the Tv set during the commercial, very bright and sharply”

-Single frame from toy story 3 took 16 hours to render
-Using one computer it would have taken 1648 days to render (just over 4.5 years)
-Raytracing was available at the time but wouldn’t be worth the rendering time required at the time.
-The average viewer never even noticed to poor reflection quality

Shadow silhouette mapping

Soft dynamic shadows are still an unrealistic option when it comes to real time rendering. An alternative low taxing method for creating shadows in games is through the use of a silhouette shadow map.
This is pretty simple.
Animators use silhouettes regularly to create dramatic poses, but this time the silhouette of a character is blacked out and projected on the ground relative to the dominant light source.
Depending on the detail of your shadow map, it may skew and stretched out of proportion in ways that pixelate the shadow.
The best way to fix this is to blur the shadow to hide any imperfections.

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